What I've seen, is the older they are, the more issues they have. I've worked on a few and have owned one. A friend asked me lately what I thought about trading his off for a BHP. Given this choice, I suggested that he trade it. Eventually they will all face issues particualr to them. ....
However,
I understand that when they get bad enough, they can be converted to 7600's and you can go on for another life span.
Be Safe !!!